Phenotypic characterization of air-borne pink pigmented facultative methylotrophic bacteria from a high vehicular traffic density environment in Manila, Philippines

A total of 40 air-borne pink pigmented facultative methylotrophic (PPFM) bacterial isolates were sampled from Taft Avenue, Manila using the settle plate method. These isolates were observed to be Gram negative, rod-shaped cells that either occurred singly or in rosettes. Special staining revealed that they exhibit poly-β-hydroxybutyrate granules but not capsules nor endospores. All isolates were found to be motile and obligate aerobic bacteria. Biochemical tests showed that they were positive for urease, catalase, amylase, collagenase and oxidase enzymes. Variations in colony morphology were observed in PPFM bacterial isolates grown in ammonium mineral salts agar and nutrient agar, while all of the isolates exhibited echinulate growth patterns in glycerol-peptone agar and tryptic-soy agar slants. Temperature tolerance tests revealed that the isolates could grow at 250C and 370C but not at 20C and 450C. Salt tolerance test showed that they cannot withstand salt concetration as low as 2% NaC1 and above. Based on the observed morphological, biochemical and physiological properties, the isolates were identified to belong to the genus Methylobacterium